Functional electrical stimulation therapy for restoration of motor function after spinal cord injury and stroke: a review

Table 1 Stimulation electrodes with different levels of invasiveness

Type	Typical current	Advantages	Disadvantages
Invasive
Implanted	25 mA	High stimulation specificity	Require surgery
Implanted	25 mA	Suitable for long-term use	Placement cannot be modified after implantation
Percutaneous	25 mA	High stimulation specificity	Require surgery
Percutaneous	25 mA	Suitable for short-term use
Non-invasive
Transcutaneous (surface)	2 mA–120 mA	Do not require surgery	Unsuitable for stimulation of deep muscles
Transcutaneous (surface)	2 mA–120 mA	Easy to reposition	Often require higher stimulation current